The present invention relates to a spatial light modulator suitable for display apparatus, camera apparatus and optical computers and the like, and more particularly, to an improved spatial light modulator with respect to two items of information.
A conventional spatial light modulator is shown in FIG. 1. In the figure, a spatial light modulator 11 has laminates of a photoconductive layer 5 and a light modulation layer 7 between transparent electrodes 1 and 3. A drive source 9 is connected between the transparent electrodes 1 and 3.
Information writing is performed by irradiation of a writing light that includes the information, as shown by an arrow F1. More specifically, the electric resistance of the photoconductive layer 5 changes in accordance with optical intensity of the writing light, and a charge image corresponding to the information that is to be written is formed at the boundary between the photoconductive layer 5 and the light modulation layer 7.
The reading of the written information is performed by allowing a read light to pass through the spatial light modulator 11 as shown by the arrow F2. The light modulation layer 7 is applied with an electric field caused by the charge image that has been formed corresponding with the write information, and is in a status where light modulation is performed so as to correspond to the intensity of this field. Because of this, the reading light is modulated in its intensity or polarization plane corresponding to the information written in the light modulation layer 7 and light-to-light conversion is performed.
However, in such conventional technology, when two items of different information are to be handled at the same time, it is necessary to provide two spatial light modulators and it is necessary to have a synthesis operation of the read images.